The present invention relates generally to automatic guidance control systems for providing signals to control the direction of travel of a moving vehicle to follow a prescribed path. More particularly, the present invention relates to a guidance control system for providing visual cues to augment operator control for guiding agricultural vehicles while following a previously plowed furrow or guiding means in a field under cultivation.
The increase of the average farm size and the need to produce the maximum amount of agricultural products from a given amount of acreage at a minimum cost has resulted in the use of larger farm equipment and the need for greater efficiency. The guidance of this larger, and usually wider, equipment while in the field can have considerable effect upon the machine's effective field capacity and thus its field efficiency. Some agricultural operations require extreme guidance accuracy due to various reasons. Each plowed furrow should be parallel with all other furrows and spaced at very accurate separation distances. Another example concerns applications of herbicide. If two "passes" lap over one another possible damage to the crop may result, or, conversely, a strip completely missed results in no weed control.
Many methods of guidance have been utilized to either augment or replace the equipment operator. Systems for remotely guiding vehicles by operator control or in combination with automatic mechanical-hydraulic guidance mechanisms which follow a pre-established path are well known in the art. Remote control and other systems providing fully automatic guidance of an agricultural vehicle, such as a tractor, frequently utilize complex electric or electro-hydraulic servo control mechanisms along with other electronic circuitry. Other systems rely on electronic sensors for detecting guide markers previously emplanted in the ground. In the agricultural environment, these largely electronic systems require much cost and maintenance to assure their reliability over extended periods of use. Repair of these units typically require a person with an electronics background and associated electronic support equipment and tools. Furthermore, the front end cost of such guidance apparatus is substantial.
U.S. Pat. No. 3,797,602 entitled "Vehicle Guidance System" issued to Harry H. Sumida on Mar. 19, 1974, discloses a mechanical guidance apparatus which overcomes many of the problems associated with electronic systems dicusses above. However, there are many problems associated with Sumida.
Sumida discloses a trailing wheel apparatus followng a precut trench. A separate trench cutting mechanism is utilized to provide the precut trench. As the trailing wheel apparatus is towed, centered directly behind the tractor, the trench cutting mechanism must be extended a substantial distance beyond the side of the farm implement being used so that guide trenches for a succeeding path are formed so as to assure there will be no overlap in the area of the field being worked by the implement. This makes the implement bulky and less easy to maneuver. Further since the trench cutting mechanism is passive in nature and operatively engages the ground at all times while the implement is working the field, more pulling power is required of the tractor.
U.S. Pat. No. 4,484,647 entitled "Apparatus for Guiding a Vehicle Pulling an Implement Including Trench Forming and Following Means" issued to John McGraw on Nov. 27, 1984, discloses an apparatus which overcomes some of the problems of Sumida at the expense of being more complicated. McGraw provides an apparatus comprising a wheel which follows a precut trench and includes an integral trench cutting member which can be hydraulically lowered into cutting position or raised to a non-cutting position.